Study of a second-order hadronic process: The π-p→φn reaction

We present a semiquantitative analysis of the energy and momentum-transfer dependence of the truly "second-order" hadronic reaction π-p→φn, where the input is provided by certain "first-order" hadronic processes. Unitarity, analyticity and crossing determine both the imaginary and real parts of the amplitudes without the explicit use of dispersion relations. Dual unitarization naturally explains the marked difference between unnatural- and natural-parity exchanges, the former being responsible for the anomalous s and t behavior of π-p→φn.